Myosin II Function and Comparison

Microfilaments are involved in cell shape and movement, interact with myosin for muscle contraction, and are involved in cell migration, amoeboid movement, and cytoplasmic streaming.

Actin is the protein building block of microfilaments, folding into a globular-shaped molecule that can bind ATP or ADP.

G-actin monomers self-assemble into microfilaments through a lag phase and elongation phase, similar to tubulin assembly, forming F-actin filaments composed of two linear strands of polymerized G-actin wound into a helix.

<p>All the actin monomers in a microfilament have the same orientation, with a 'pointed end' and a 'barbed end'.</p> Signup and view all the answers

<p>Myosin interacts with microfilaments to facilitate muscle contraction and cell movement.</p> Signup and view all the answers

<p>Cytoplasmic streaming is the generation of currents in the cytoplasm, which is facilitated by microfilaments.</p> Signup and view all the answers

<p>Microfilaments are involved in cell migration, amoeboid movement, and cytoplasmic streaming, facilitating cell crawling and chemotaxis.</p> Signup and view all the answers

<p>The structural core of microvilli is formed by microfilaments.</p> Signup and view all the answers

<p>To pull arrays of actin filaments together, resulting in contraction of a cell or group of cells</p> Signup and view all the answers

<p>They move toward the plus ends of actin filaments</p> Signup and view all the answers

<p>Kinesins operate alone or in small numbers to transport vesicles, while myosin II molecules work in large arrays to mediate muscle contraction</p> Signup and view all the answers

<p>The sliding filament model states that muscle contraction is due to thin filaments sliding past thick filaments, with no change in length of either</p> Signup and view all the answers

<p>Cross-bridges are formed between the F-actin of thin filaments and myosin heads of thick filaments, and they dissociate rapidly, requiring lots of ATP</p> Signup and view all the answers

<p>They move short distances but operate in large arrays, in some cases billions of motors working together</p> Signup and view all the answers

<p>A muscle fiber consists of parallel myofibrils, each of which is divided into repeating units called sarcomeres</p> Signup and view all the answers

<p>About 12-15 nm</p> Signup and view all the answers

<p>They act as an antenna for the cell.</p> Signup and view all the answers

<p>9 + 0</p> Signup and view all the answers

<p>Ciliopathies, such as deafness and left-right asymmetry reversals.</p> Signup and view all the answers

<p>They interact with and exert force on actin microfilaments, facilitating processes such as muscle contraction, cell movement, phagocytosis, and vesicle transport.</p> Signup and view all the answers

<p>Primary cilia dyskinesia</p> Signup and view all the answers

<p>They are involved in the development of primary cilia.</p> Signup and view all the answers

<p>It is associated with the photoreceptor of the retina.</p> Signup and view all the answers

<p>They lack the central pair and are non-motile.</p> Signup and view all the answers

<p>The primary function of myosin II is to pull arrays of actin filaments together, resulting in contraction of a cell or group of cells. It differs from kinesins in that myosin II molecules move short distances but operate in large arrays, whereas kinesins operate alone or in small numbers to transport vesicles over large distances.</p> Signup and view all the answers

<p>The sliding filament model proposes that muscle contraction occurs when thin filaments slide past thick filaments, resulting in shortening of sarcomeres and muscle fiber contraction, with no change in length of either filament.</p> Signup and view all the answers

<p>Myosin II molecules move toward the plus ends of actin filaments, resulting in the shortening of sarcomeres and muscle fiber contraction.</p> Signup and view all the answers

<p>Cross-bridges are formed between the F-actin of thin filaments and myosin heads of thick filaments, allowing for the sliding of filaments and resulting in muscle contraction.</p> Signup and view all the answers

<p>A muscle fiber consists of numerous myofibrils, each divided into repeating units called sarcomeres. Muscle contraction occurs when myosin II molecules pull actin filaments together, resulting in the shortening of sarcomeres and muscle fiber contraction.</p> Signup and view all the answers

<p>Myosin II molecules have globular domains that walk along actin filaments, using ATP hydrolysis to change their shape, allowing for the sliding of filaments and resulting in muscle contraction.</p> Signup and view all the answers

<p>The polarity of actin monomers in a microfilament allows for the directional movement of myosin II molecules, resulting in the shortening of sarcomeres and muscle fiber contraction.</p> Signup and view all the answers

<p>The structure of actin filaments, with their polarity and dynamic assembly, allows for the interaction with myosin II molecules, resulting in the sliding of filaments and muscle contraction.</p> Signup and view all the answers

<p>Myosin II generates force through a power stroke, where the myosin head binds to an actin filament and produces a conformational change, resulting in movement of the actin filament.</p> Signup and view all the answers

<p>Actin filaments regulate the movement of myosin II motors by providing a track for the motors to move along, and the polarity of the actin filament determines the direction of movement.</p> Signup and view all the answers

<p>The 'barbed end' is the fast-growing end of the filament, where actin monomers are added, while the 'pointed end' is the slow-growing end, where actin monomers are removed.</p> Signup and view all the answers

<p>Myosin VI is involved in endocytosis and exocytosis, while myosin VII is involved in melanosome transport; they differ in their motor domains and regulation.</p> Signup and view all the answers

<p>Tropomyosin stabilizes actin filaments and regulates access of myosin motors to the filament, controlling muscle contraction and cell movement.</p> Signup and view all the answers

<p>Kinesin motors transport organelles along microtubules, while myosin motors move along actin filaments, together regulating organelle transport and cell migration.</p> Signup and view all the answers

<p>The actin-binding domain binds to actin filaments, allowing myosin II motors to move along the filament and generate force.</p> Signup and view all the answers

<p>Post-translational modifications such as phosphorylation regulate myosin II motor activity, controlling its binding to actin filaments and force generation.</p> Signup and view all the answers

<p>It indicates that primary cilia lack the central pair and therefore do not move.</p> Signup and view all the answers

<p>Myosins interact with actin microfilaments through ATP-dependent motor activity, exerting force on the microfilaments.</p> Signup and view all the answers

<p>Defects in primary cilia development can result in ciliopathies, such as deafness and left-right asymmetry reversals.</p> Signup and view all the answers

<p>Dynein is involved in the movement of primary cilia, and its loss results in primary cilia dyskinesia, leading to disorders such as Kartagener syndrome.</p> Signup and view all the answers

<p>Primary cilia play a crucial role in embryonic patterning and organogenesis, and their dysfunction can lead to developmental disorders.</p> Signup and view all the answers

<p>Myosins facilitate the movement of vesicles and membranes during phagocytosis, allowing cells to engulf and internalize foreign particles.</p> Signup and view all the answers

<p>Primary cilia are commonly found on the apical surface of epithelial cells, where they play a crucial role in sensing and responding to external stimuli.</p> Signup and view all the answers

<p>Genes associated with ciliogenesis regulate the formation and development of primary cilia, ensuring their proper structure and function.</p> Signup and view all the answers

<p>Myosin II's primary function is to pull arrays of actin filaments together, resulting in cell or group of cells contraction. It differs from kinesins in that kinesins operate alone or in small numbers to transport vesicles over large distances, whereas myosin II molecules move short distances but operate in large arrays to mediate muscle contraction.</p> Signup and view all the answers

<p>The sliding filament model explains muscle contraction as a result of thin filaments sliding past thick filaments, with no change in length of either. This movement is facilitated by cross-bridges formed between the F-actin of thin filaments and myosin heads of thick filaments.</p> Signup and view all the answers

<p>The polarity of actin monomers in a microfilament is significant because it determines the direction of myosin II movement. Myosin II moves toward the plus ends of actin filaments, resulting in muscle contraction.</p> Signup and view all the answers

<p>Myosin II molecules operate in large arrays, moving short distances along actin filaments. Cross-bridges formed between myosin heads and actin filaments are essential for force generation during muscle contraction.</p> Signup and view all the answers

<p>A muscle fiber consists of parallel myofibrils, each divided into repeating units called sarcomeres. During muscle contraction, myosin II molecules slide along actin filaments, resulting in sarcomere shortening and muscle contraction.</p> Signup and view all the answers

<p>Myosin II molecules have globular domains that walk along actin filaments, using ATP hydrolysis to change their shape and generate force during muscle contraction.</p> Signup and view all the answers

<p>Myosin II generates force during muscle contraction through the formation of cross-bridges with actin filaments, which is fueled by ATP hydrolysis.</p> Signup and view all the answers

<p>The polarity and dynamic structure of actin filaments enable myosin II molecules to move along them, generating force during muscle contraction.</p> Signup and view all the answers

<p>Primary cilia function as antennae, sensing and responding to external stimuli. They have a '9 + 0' axoneme structure, lacking the central pair, and do not move.</p> Signup and view all the answers

<p>Myosins are ATP-dependent motors that interact with and exert force on actin microfilaments, functioning in various cellular events such as muscle contraction, cell movement, phagocytosis, and vesicle transport.</p> Signup and view all the answers

<p>Defects in primary cilia development can result in disorders such as deafness and left-right asymmetry reversals, known as ciliopathies.</p> Signup and view all the answers

<p>Dynein is involved in the movement of primary cilia, and its loss can result in primary cilia dyskinesia, leading to disorders such as Kartagener syndrome.</p> Signup and view all the answers

<p>RPE65 is a gene associated with specific ciliated cells, such as the photoreceptor of the retina.</p> Signup and view all the answers

<p>Myosins assist in the process of phagocytosis by facilitating the movement of vesicles and the engulfment of particles, which is essential for cellular defense and clearance of foreign substances.</p> Signup and view all the answers

<p>Primary cilia are commonly found on the apical surface of epithelial cells, where they play a crucial role in sensing and responding to external stimuli.</p> Signup and view all the answers

<p>The '9 + 0' axoneme structure is characteristic of primary cilia, distinguishing them from other cilia, which have a '9 + 2' structure. This difference in structure reflects their distinct functions.</p> Signup and view all the answers

<p>Myosin II generates force through the power stroke mechanism, where the myosin head binds to the actin filament and undergoes a conformational change, producing a force-generating movement. This mechanism is dependent on the polarity of actin monomers in a microfilament, with the 'barbed end' having a higher affinity for myosin binding and the 'pointed end' having a lower affinity.</p> Signup and view all the answers

<p>Kinesins and myosin II are both motor proteins, but they have distinct structures and functions. Kinesins are involved in anterograde transport, moving along microtubules, whereas myosin II is involved in muscle contraction and cell migration, moving along actin filaments. Kinesins have a single motor domain, whereas myosin II has a double-headed structure, allowing for processive movement. Additionally, kinesins move towards the plus end of microtubules, whereas myosin II moves towards the barbed end of actin filaments.</p> Signup and view all the answers

<p>Actin-binding proteins, such as tropomyosin, regulate actin filament dynamics by modulating the accessibility of actin filaments to myosin motors. This regulation affects the activity of myosin motors, influencing cell migration and chemotaxis. Tropomyosin, for example, blocks the binding of myosin to actin filaments, thereby inhibiting muscle contraction and promoting cell migration.</p> Signup and view all the answers

<p>The 'barbed end' of an actin filament has a higher affinity for myosin binding, promoting myosin motor activity, whereas the 'pointed end' has a lower affinity, inhibiting myosin motor activity. This polarity of actin monomers determines the direction of movement, with myosin motors moving towards the barbed end, generating force and promoting cell migration.</p> Signup and view all the answers

<p>Myosin VI and myosin VII motors differ in their function and regulation. Myosin VI is involved in retrograde transport, moving towards the minus end of actin filaments, whereas myosin VII is involved in cell migration and chemotaxis, moving towards the barbed end of actin filaments. Myosin VI is regulated by binding to cargo molecules, whereas myosin VII is regulated by phosphorylation. These differences influence the direction and speed of movement, with implications for cellular events, such as transport and migration.</p> Signup and view all the answers

<p>The sliding filament model explains muscle contraction by proposing that myosin motors move along actin filaments, generating force through the power stroke mechanism. This model is based on the structure of actin filaments, with their 'barbed end' and 'pointed end', and the double-headed structure of myosin motors, allowing for processive movement.</p> Signup and view all the answers

<p>Post-translational modifications, such as phosphorylation, regulate myosin II motor activity by modulating the binding of myosin to actin filaments. Phosphorylation can either activate or inhibit myosin motor activity, depending on the specific phosphorylation site. This regulation influences cellular events, such as muscle contraction and cell migration, by modulating the force generated by myosin motors.</p> Signup and view all the answers

<p>Tropomyosin regulates actin filament dynamics by modulating the accessibility of actin filaments to myosin motors. This regulation affects the activity of myosin motors, influencing cell migration and chemotaxis. Tropomyosin can either promote or inhibit cell migration, depending on the specific context and the type of tropomyosin isoform.</p> Signup and view all the answers